Two polyamine antagonists are scheduled for clinical trial here at RPCI-- one, a polyamine analog, N1 ,N11-diethylnorspermine (DENSPM), which deregulates polyamine homeostasis and potently inhibits tumor growth in preclinical model systems and the other, a polyamine inhibitor, CGP-48664, which target the polyamine biosynthetic enzyme, S-adenosylmethionine decarboxylase, depletes polyamine pools an inhibits tumor growth in vivo. Both agents have been rationally developed in two separate drug discover initiatives with the active involvement of this laboratory. Although not sequentially linked, the Specific Aims of this proposal are unified by the common goal of optimizing the clinical development of these promising new solid tumor therapies. In this context, the following activities are proposed: Aim 1, to validate the preclinically-indicated mode of action of both DENSPM and CGP-48664 in solid tumors obtained from patients treated with DENSPM or CGP48664; Aim 2, to examine the underlying regulatory mechanisms involved in the potent and heterogeneous induction of a polyamine catabolizing enzyme by DENSPM human melanoma cell lines--a response which appears from preclinical studies to be a critical in vivo determinant of antitumor activity of the analog; when technically possible findings ; Aim 3 to follow up on a recently observed association between distinct disturbances in polyamine homeostasis and the multidrug resistance phenotype in human melanoma cell lines--specifically, we will examine the basis for this apparent linkage and the therapeutic potential of polyamine antagonists in addressing multidrug resistance. Methodologies to be used in these studies include human cell culture techniques, biochemical enzyme assays, HPLC detection of polyamines and their analogs, rhodamine retention assays, flow cytometry Northern blots, Southern blots, nuclear run-on assays, mRNA half-life determinations and in vitro translation assays.